17/08/2026
A full blood count can come back completely normal while your iron stores are running on empty.
That’s because haemoglobin, the thing a standard blood count measures, is the last thing to drop. Your body will strip its reserves first and keep haemoglobin propped up for a long time. The test that shows the reserves is ferritin, and it isn’t always included.
This matters most for anyone who menstruates, where low iron is common and often runs for years before it shows up on a basic panel. Fatigue, breathlessness on stairs, cold hands, hair shedding, brain fog. All of it gets put down to being busy.
Vitamin D is worth knowing about too. Deficiency is genuinely common here, particularly between October and March, and more so if you have darker skin or cover up. But most people supplement it without ever having it measured, which means if it wasn’t the problem, you’ve spent months not finding out what was.
Thyroid, B12, blood sugar and sleep quality all sit on the same list.
The point isn’t that your tiredness is nothing. It’s that tiredness has a lot of possible causes and only a few of them show up on the panel you’re most likely to be given.
If you’ve been tired for months and been told everything looks fine, it’s reasonable to ask what was actually tested.